[ios] Use WebStateList to back the tab grid.

ios/clean/chrome/browser/ui/tab_grid/tab_grid_coordinator.mm

Index: ios/clean/chrome/browser/ui/tab_grid/tab_grid_coordinator.mm
diff --git a/ios/clean/chrome/browser/ui/tab_grid/tab_grid_coordinator.mm b/ios/clean/chrome/browser/ui/tab_grid/tab_grid_coordinator.mm
index 1b620951c1f70b2fac738686876e148534d96095..9362a1478e51b040675be78acb9f08263eb321f6 100644
--- a/ios/clean/chrome/browser/ui/tab_grid/tab_grid_coordinator.mm
+++ b/ios/clean/chrome/browser/ui/tab_grid/tab_grid_coordinator.mm
@@ -21,6 +21,7 @@
 #import "ios/clean/chrome/browser/ui/tab/tab_coordinator.h"
 #import "ios/clean/chrome/browser/ui/tab_grid/tab_grid_view_controller.h"
 #import "ios/shared/chrome/browser/coordinator_context/coordinator_context.h"
+#import "ios/shared/chrome/browser/tabs/web_state_list.h"
 #import "ios/web/public/navigation_manager.h"
 #include "ios/web/public/web_state/web_state.h"
 #import "net/base/mac/url_conversions.h"
@@ -33,13 +34,10 @@
 @interface TabGridCoordinator ()<TabGridDataSource,
                                  SettingsCommands,
                                  TabCommands,
-                                 TabGridCommands> {
-  std::vector<std::unique_ptr<web::WebState>> _webStates;
-  size_t _activeWebStateIndex;
-}
-
+                                 TabGridCommands>
 @property(nonatomic, strong) TabGridViewController* viewController;
 @property(nonatomic, weak) SettingsCoordinator* settingsCoordinator;
+@property(nonatomic, readonly) WebStateList& webStateList;
 @end
 
 @implementation TabGridCoordinator
@@ -55,9 +53,13 @@
     web::WebState::CreateParams webStateCreateParams(browser->browser_state());
     std::unique_ptr<web::WebState> webState =
         web::WebState::Create(webStateCreateParams);
-    _webStates.push_back(std::move(webState));
+    self.webStateList.InsertWebState(0, webState.release(), nullptr);
   }
-  _activeWebStateIndex = 0;
+  self.webStateList.ActivateWebStateAt(0);
+}
+
+- (WebStateList&)webStateList {
+  return self.browser->web_state_list();
 }
 
 #pragma mark - BrowserCoordinator
@@ -80,15 +82,12 @@
 
 #pragma mark - TabGridDataSource
 
-- (NSUInteger)numberOfTabsInTabGrid {
-  return static_cast<NSUInteger>(_webStates.size());
+- (int)numberOfTabsInTabGrid {
+  return self.webStateList.count();
 }
 
-- (NSString*)titleAtIndex:(NSInteger)index {
-  size_t i = static_cast<size_t>(index);
-  DCHECK(i < _webStates.size());
-  web::WebState* webState = _webStates[i].get();
-  GURL url = webState->GetVisibleURL();
+- (NSString*)titleAtIndex:(int)index {
+  GURL url = self.webStateList.GetWebStateAt(index)->GetVisibleURL();
   NSString* urlText = @"<New Tab>";
   if (url.is_valid()) {
     urlText = base::SysUTF8ToNSString(url.spec());
@@ -96,27 +95,30 @@
   return urlText;
 }
 
-- (NSInteger)indexOfActiveTab {
-  return static_cast<NSInteger>(_activeWebStateIndex);
+- (int)indexOfActiveTab {
+  return self.webStateList.active_index();
 }
 
 #pragma mark - TabCommands
 
 - (void)showTabAtIndexPath:(NSIndexPath*)indexPath {
   TabCoordinator* tabCoordinator = [[TabCoordinator alloc] init];
-  size_t index = static_cast<size_t>(indexPath.item);
-  DCHECK(index < _webStates.size());
-  tabCoordinator.webState = _webStates[index].get();
+  DCHECK_LE(indexPath.item, INT_MAX);
+  int index = static_cast<int>(indexPath.item);
+  self.webStateList.ActivateWebStateAt(index);
+  // PLACEHOLDER: The tab coordinator should be able to get the active webState
+  // on its own.
+  tabCoordinator.webState = self.webStateList.GetWebStateAt(index);
   tabCoordinator.presentationKey = indexPath;
   [self addChildCoordinator:tabCoordinator];
   [tabCoordinator start];
-  _activeWebStateIndex = index;
 }
 
 - (void)closeTabAtIndexPath:(NSIndexPath*)indexPath {
-  size_t index = static_cast<size_t>(indexPath.item);
-  DCHECK(index < _webStates.size());
-  _webStates.erase(_webStates.begin() + index);
+  DCHECK_LE(indexPath.item, INT_MAX);
+  int index = static_cast<int>(indexPath.item);
+  std::unique_ptr<web::WebState> closedWebState(
+      self.webStateList.DetachWebStateAt(index));
 }
 
 - (void)createNewTabAtIndexPath:(NSIndexPath*)indexPath {
@@ -124,7 +126,8 @@
       self.browser->browser_state());
   std::unique_ptr<web::WebState> webState =
       web::WebState::Create(webStateCreateParams);
-  _webStates.push_back(std::move(webState));
+  self.webStateList.InsertWebState(self.webStateList.count(),
+                                   webState.release(), nullptr);
 }
 
 #pragma mark - TabGridCommands
@@ -157,17 +160,19 @@
 #pragma mark - URLOpening
 
 - (void)openURL:(NSURL*)URL {
+  if (self.webStateList.active_index() == WebStateList::kInvalidIndex) {
+    return;
+  }
   [self.overlayCoordinator stop];
   [self removeOverlayCoordinator];
-  web::WebState* activeWebState = _webStates[_activeWebStateIndex].get();
+  web::WebState* activeWebState = self.webStateList.GetActiveWebState();
   web::NavigationManager::WebLoadParams params(net::GURLWithNSURL(URL));
   params.transition_type = ui::PAGE_TRANSITION_LINK;
   activeWebState->GetNavigationManager()->LoadURLWithParams(params);
   if (!self.children.count) {
-    [self showTabAtIndexPath:[NSIndexPath
-                                 indexPathForItem:static_cast<NSUInteger>(
-                                                      _activeWebStateIndex)
-                                        inSection:0]];
+    [self
+        showTabAtIndexPath:[NSIndexPath indexPathForItem:[self indexOfActiveTab]
+                                               inSection:0]];
   }
 }